Merge pull request #56 from elifesciences/tweaks

Tweaks
Start email queue SimpleDB queries.
SimpleDB email queue query sort_by and limit options.
Email queue unique item_name generator.
Fix duplicate have_timestamp in test functions and float conversion.
Basic add email to email queue.
SendQueuedEmail activity with small fix to simpleDB.py
Draft SendQueuedEmail workflow and starter.
Count items query added for email queue.
General purpose five minute cron, runs SendQueuedEmail for now.
Add a body to queued emails.
Switch AdminEmailHistory to use the email queue.
Merge pull request #58 from elifesciences/email-queue

Email queue